ISO/TS 23690:2023
(Main)Nanotechnologies — Multiwall carbon nanotubes — Determination of carbon impurity content by thermogravimetric analysis
Nanotechnologies — Multiwall carbon nanotubes — Determination of carbon impurity content by thermogravimetric analysis
This document specifies a mild oxidation method to determine the content of carbon impurities (carbon material content not in the form of CNT, including amorphous carbon and trace amountd of other types of structured carbon) less stable than multiwall carbon nanotubes (MWCNTs) by thermogravimetric analysis (TGA) under carbon dioxide atmosphere. This document is applicable to the characterization of carbon impurities content in MWCNT samples prepared by chemical vapour deposition (CVD). Measurement of carbon impurities in MWCNT samples prepared by other methods can refer to this document. This method is not applicable to functionalized MWCNT samples or MWCNT samples with encapsulant species. NOTE This method is applicable for the case of TG curves with a single-stage.
Nanotechnologies – Nanotubes de carbone multicouches – Détermination de la teneur en impureté de carbone par analyse thermogravimetrique
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TECHNICAL ISO/TS
SPECIFICATION 23690
First edition
2023-07
Nanotechnologies — Multiwall
carbon nanotubes — Determination
of carbon impurity content by
thermogravimetric analysis
Nanotechnologies – Nanotubes de carbone multicouches –
Détermination de la teneur en impureté de carbone par analyse
thermogravimetrique
Reference number
ISO/TS 23690:2023(E)
© ISO 2023
---------------------- Page: 1 ----------------------
ISO/TS 23690:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 23690:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols . 2
3.3 Abbreviated terms . 2
4 Principle . 2
5 Sample preparation .3
6 Measurement .3
6.1 Apparatus . 3
6.1.1 Thermogravimetric analyser . 3
6.1.2 Drying furnace . 3
6.1.3 Analytical balance . . 3
6.1.4 Desiccator . 3
6.2 Reagents . 3
6.2.1 Inert gas . 3
6.2.2 Carbon dioxide . 3
6.3 Measurement procedures . 3
7 Data analysis and interpretation of results . 4
8 Measurement uncertainty .5
8.1 Type A uncertainty . 5
8.2 Type B uncertainty . 5
9 Test report . 5
Annex A (informative) Repeatability test: Case study . 7
Annex B (informative) Reproducibility test: Case study.15
Annex C (informative) Detailed procedures for the analysis of the TG curve .19
Bibliography .21
iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/TS 23690:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
© ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 23690:2023(E)
Introduction
Multiwall carbon nanotubes (MWCNTs) are quasi-one-dimensional tubular carbon nanomaterials
rolled up or coaxial nested by three or more graphene sheets. The production of carbon nanotubes
(CNT) generally results in significant amounts of carbon impurities (carbon material content not in
the form of CNT, including amorphous carbon and trace amounts of other types of structured carbon),
which influence the physical and chemical properties of the nanomaterial. Therefore, the measurement
of carbon impurities content in MWCNT samples is highly desirable for the determination of their
purity.
Several methods have been reported to characterize carbon impurities in MWCNT samples,
including transmission electron microscopy (TEM), temperature programmed oxidation (TPO) and
[1][2][3][4]
thermogravimetric analysis (TGA), etc., among which TGA can provide quantitative results.
[5][6]
This technique makes use of the fact that MWCNTs are more stable than the majority of carbon
impurities, so carbon impurities less stable than MWCNTs will react firstly with carbon dioxide in
carbon dioxide atmosphere. The oxidation of carbon impurities with carbon dioxide is an endothermal
process, which prevents overheating in certain areas and restrains the reaction of MWCNTs at the same
time. Therefore, the separation between the oxidation of carbon impurities and those of MWCNTs is
[7][8][9][10]
enhanced, allowing the amount of carbon impurities less stable than MWCNTs to be calculated
from the mass loss in thermogravimetric analysis.
v
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
TECHNICAL SPECIFICATION ISO/TS 23690:2023(E)
Nanotechnologies — Multiwall carbon nanotubes
— Determination of carbon impurity content by
thermogravimetric analysis
1 Scope
This document specifies a mild oxidation method to determine the content of carbon impurities (carbon
material content not in the form of CNT, including amorphous carbon and trace amountd of other types
of structured carbon) less stable than multiwall carbon nanotubes (MWCNTs) by thermogravimetric
analysis (TGA) under carbon dioxide atmosphere.
This document is applicable to the characterization of carbon impurities content in MWCNT samples
prepared by chemical vapour deposition (CVD). Measurement of carbon impurities in MWCNT samples
prepared by other methods can refer to this document. This method is not applicable to functionalized
MWCNT samples or MWCNT samples with encapsulant species.
NOTE This method is applicable for the case of TG curves with a single-stage.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
multiwall carbon nanotube
MWCNT
multi-walled carbon nanotube
carbon nanotube composed of nested, concentric or near-concentric graphene layers with interlayer
distances similar to those of graphite
Note 1 to entry: The structure is normally considered to be many single-walled carbon nanotubes nesting each
other and would be cylindrical for small diameters but tends to have a polygonal cross-section as the diameter
increases.
[11]
[SOURCE: ISO/TS 80004-3:2020, 3.3.6 ]
3.1.2
amorphous carbon
carbon material without long-range crystalline order
[12]
[SOURCE: IUPAC, Compendium of Chemical Terminology ]
1
© ISO 2023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/TS 23690:2023(E)
3.2 Symbols
T temperature of the peak on DTG curve (°C)
o
w mass percentage (%) of the sample at 300 °C
300
w mass percentage (%) of the sample at temperature T
e e
ΔH is the enthalpy change
3.3 Abbreviated terms
CO carbon dioxide
2
CVD chemical vapour deposition
DTG derivative thermogravimetric
MWCNT multiwall carbon nanotube
TG thermogravimetric
TGA thermogravimetric analysis
4 Principle
Thermogravimetric analysis measures the change in mass of a material as a function of temperature. In
order to accomplish this, TGA requires the precise measurements of mass, temperature and temperature
change. The change in mass of a material relates to change in composition and structure of the material.
Observed mass changes with temperature increases may result from the removal of absorbed moisture,
solvent residues, chemically bound moieties and/or the thermal or oxidative decomposition of product.
[13]
The experiments are carried out in an inert or oxidising atmosphere. The recorded mass change
as a function of temperature is a thermogravimetric (TG) curve. Mass change and the extent of these
[14]
changes of a material in a TG curve are indicators of the thermal stability of the material. Derivative
thermogravimetric (DTG) curve is a display of the first derivative of thermogravimetry data with
[15]
respect to temperature or time .
The method specified in this document is based on different reactivity of MWCNTs and carbon impurities
under carbon dioxide (CO ) atmosphere during heating. Carbon dioxide works as a mild oxidant to first
2
oxidize carbon impurities less stable than MWCNTs. Moreover, the reaction between carbon impurities
[7][8][9]
and CO absorbs heat from environment, which prevents local overheating, and thus enhances
2
the separation of carbon impurities and MWCNTs. The amount of carbon impurities in MWCNT samples
can be calculated from the mass loss in thermogravimetric analyser. See the reaction formula below.
C + CO → 2 CO ; ΔH > 0
(s) 2(g) (g)
where
C is the carbon impurities in solid state;
(s)
CO is the carbon dioxide in gaseous state;
2(g)
CO is the carbon monoxide in gaseous state;
(g)
ΔH is the enthalpy change.
2
© ISO 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/TS 23690:2023(E)
5 Sample preparation
MWCNT sample should be of good quality. MWCNT sample is first placed in a thermostatic vacuum
[16]
drying furnace for 2 h at 150 °C to remove unwanted volatile components. Then the sample is
transferred to a desiccator to cool down to room temperature and it is stored there until used.
6 Measurement
6.1 Apparatus
6.1.1 Thermogravimetric analyser
Thermogravimetric analyser should consist of a furnace, which is capable of heating from room
temperature to 1 000 °C or above. Heating rate during experiment should be controlled by temperature
[14]
programme set in software .
−1 −1
The linear heating rate should be controllable in the range from 1 °C min to 50 °C min . The balance
sensitivity should be at least 1 μg, and the temperature controller sensitivity less than or equal to
0,01 °C.
A crucible should be used as a sample container. The crucible is generally made of alumina, platinum,
quartz or other materials, which does not change or react under the measurement conditions.
6.1.2 Drying furnace
A drying furnace capable of controlled heating to at least 150 °C is used.
6.1.3 Analytical balance
An analytical balance capable of weighing 0,1 mg or lower is used.
6.1.4 Desiccator
A dessicator containing a desiccant such as dried silica gel impregnated with cobalt chloride is used.
The drying agent shall not react with MWCNT samples.
6.2 Reagents
6.2.1 Inert gas
Dry, commercially available inert gas, such as nitrogen gas or argon gas, with minimum volume fraction
of 99,999 % should be used in the measurement.
6.2.2 Carbon dioxide
Dry, commercially available carbon dioxide gas with minimum volume fraction of 99,999 % should be
used in the measurement.
6.3 Measurement procedures
The thermogravimetric analyser should be calibrated according to the manufacturer’s protocol to
ensure proper temperature and mass measurement.
a) Turn on the thermogravimetric analyser and wait until equilibrium is reached. Then inert gas and
carbon dioxide gas are introduced.
3
© ISO 2023 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/TS 23690:2023(E)
b) Obtain a baseline correction file using empty crucibles at the same experiment conditions to be
used for the MWCNT sample. Specifically, set the flow rate of gas to the furnace according to the
−1 −1
instrument type. The recommended inert gas flow is 10 ml min to 20 ml min and carbon dioxide
−1 −1 −1
gas flow is 20 ml min to 40 ml min ; set the heating rate as 10 °C min within the temperature
range from room temperature to 1 000 °C.
c) Weigh an appropriate amount of MWCNT sample (3 mg to 5 mg) using an analytical balance and
transfer the sample into the crucible.
d) Before starting the measurement, keep the MWCNT sample in a closed thermogravimetric analyser
under a gas flow for at least 15 min and wait until the signal (mass, temperature, gas flow) is stable.
e) Test the sample under
...
FINAL
TECHNICAL ISO/DTS
DRAFT
SPECIFICATION 23690
ISO/TC 229
Nanotechnologies — Multiwall
Secretariat: BSI
carbon nanotubes — Determination
Voting begins on:
2023-04-14 of carbon impurity content by
thermogravimetric analysis
Voting terminates on:
2023-06-09
Nanotechnologies – Nanotubes de carbone multicouches –
Détermination de la teneur en impureté de carbone par analyse
thermogravimetrique
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/DTS 23690:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 1 ----------------------
FINAL
TECHNICAL ISO/DTS
DRAFT
SPECIFICATION 23690
ISO/TC 229
Nanotechnologies — Multiwall
Secretariat: BSI
carbon nanotubes — Determination
Voting begins on:
of carbon impurity content by
thermogravimetric analysis
Voting terminates on:
Nanotechnologies – Nanotubes de carbone multicouches –
Détermination de la teneur en impureté de carbone par analyse
thermogravimetrique
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
ISO copyright office
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CP 401 • Ch. de Blandonnet 8
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
CH-1214 Vernier, Geneva
DOCUMENTATION.
Phone: +41 22 749 01 11
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: copyright@iso.org
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/DTS 23690:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN
DARDS TO WHICH REFERENCE MAY BE MADE IN
ii
© ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 2 ----------------------
ISO/DTS 23690:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols . 2
3.3 Abbreviated terms . 2
4 Principle . 2
5 Sample preparation .3
6 Measurement .3
6.1 Apparatus . 3
6.1.1 Thermogravimetric analyser . 3
6.1.2 Drying furnace . 3
6.1.3 Analytical balance . . 3
6.1.4 Desiccator . 3
6.2 Reagents . 3
6.2.1 Inert gas . 3
6.2.2 Carbon dioxide . 3
6.3 Measurement procedures . 3
7 Data analysis and interpretation of results . 4
8 Measurement uncertainty .5
8.1 Type A uncertainty . 5
8.2 Type B uncertainty . 5
9 Test report . 5
Annex A (informative) Repeatability test: Case study . 7
Annex B (informative) Reproducibility test: Case study.18
Annex C (informative) Detailed procedures for the analysis of the TG curve .24
Bibliography .26
iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/DTS 23690:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and nongovernmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However,
implementers are cautioned that this may not represent the latest information, which may be
obtained from the patent database available at www.iso.org/patents. ISO shall not be held
responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
© ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/DTS 23690:2023(E)
Introduction
Multiwall carbon nanotubes (MWCNTs) are quasi-one-dimensional tubular carbon nanomaterials
rolled up or coaxial nested by three or more graphene sheets. The production of carbon nanotubes
(CNT) generally contains significant amounts of carbon impurities (carbon material content not in the
form of CNT, include amorphous carbon and trace amount of other types of structured carbon), which
influence the physical and chemical properties of the nanomaterial. Therefore, the measurement of
carbon impurities content in MWCNT samples is highly desired for the determination of its purity.
Several methods have been reported to characterize carbon impurities in MWCNT samples,
including transmission electron microscopy (TEM), temperature programmed oxidation (TPO) and
[1][2][3][4]
thermogravimetric analysis (TGA), etc., among which TGA can provide quantitative results.
[5][6]
This technique takes use of the fact that MWCNTs are more stable than the majority of carbon
impurities, so carbon impurities less stable than MWCNTs will react firstly with carbon dioxide in
carbon dioxide atmosphere. The oxidation of carbon impurities with carbon dioxide is an endothermal
process, which prevents overheating in certain area and restrains the reaction of MWCNTs at the same
[7]
time. Therefore, the separation of oxidation of carbon impurities and that of MWCNTs are enhanced,
[8][9][10]
allowing the amount of carbon impurities less stable than MWCNTs to be calculated from the
mass loss in thermogravimetric analysis.
v
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
TECHNICAL SPECIFICATION ISO/DTS 23690:2023(E)
Nanotechnologies — Multiwall carbon nanotubes
— Determination of carbon impurity content by
thermogravimetric analysis
1 Scope
This document specifies a mild oxidation method to determine the content of carbon impurities (carbon
material content not in the form of CNT, include amorphous carbon and trace amount of other types
of structured carbon) less stable than multiwall carbon nanotube (MWCNT) by thermogravimetric
analysis (TGA) under carbon dioxide atmosphere.
This document is applicable to the characterization of carbon impurities content in MWCNT samples
prepared by chemical vapour deposition (CVD). Measurement of carbon impurities in MWCNT samples
prepared by other method can refer to this document. This method is not applicable to functionalized
MWCNT samples or MWCNT samples with encapsulant species.
NOTE This method is applicable for the case of TG curve with a singlestage.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
multiwall carbon nanotube
MWCNT
multi-walled carbon nanotube
carbon nanotube composed of nested, concentric or near-concentric graphene layers with interlayer
distances similar to those of graphite
Note 1 to entry: The structure is normally considered to be many single-walled carbon nanotubes nesting each
other and would be cylindrical for small diameters but tends to have a polygonal cross-section as the diameter
increases.
[11]
[SOURCE: ISO/TS 800043:2020, 3.3.6 ]
3.1.2
amorphous carbon
carbon material without long-range crystalline order
[12]
[SOURCE: IUPAC, Compendium of Chemical Terminology ]
1
© ISO 2023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/DTS 23690:2023(E)
3.2 Symbols
T temperature of the peak on DTG curve (°C)
o
w mass percentage (%) of the sample at 300 °C
300
w mass percentage (%) of the sample at temperature T
e e
ΔH is the enthalpy change .
3.3 Abbreviated terms
CO carbon dioxide
2
CVD chemical vapour deposition
DTG derivative thermogravimetric
MWCNT multiwall carbon nanotube
TG thermogravimetric
TGA thermogravimetric analysis
4 Principle
Thermogravimetric analysis measures the change in mass of a material as a function of temperature.
In order to accomplish this, TGA requires the precise measurements of mass, temperature and
temperature change. The change in mass of a material relates to change in composition and structure
of the material. Observed mass changes with temperature increases may result from the removal of
absorbed moisture, solvent residues, chemically bound moieties and/or the thermal or oxidative
[13]
decomposition of product. Experiment carries out in an inert or oxidising atmosphere. The recorded
mass change as a function of temperature is a thermogravimetric (TG) curve. Mass change and the
[14]
extent of this changes of a material in TG curve are indicators of the thermal stability of the material.
Derivative thermogravimetric (DTG) curve is a display of the first derivative of thermogravimetry data
[15]
with respect to temperature or time .
The method specified in this document based on different reactivity of MWCNTs and carbon impurities
under carbon dioxide (CO ) atmosphere during heating. Carbon dioxide works as mild oxidant to first
2
oxidize carbon impurities less stable than MWCNTs. Moreover, the reaction between carbon impurities
[7][8][9]
and CO absorbs heat from environment, which prevents local overheating, and thus enhance the
2
separation of carbon impurities and MWCNTs. The amount of carbon impurities in MWCNT samples
can be calculated from the mass loss in thermogravimetric analyser. See the reaction formula below.
C + CO → 2 CO ; ΔH >0
(s) 2(g) (g)
where
C is the carbon impurities in solid state;
(s)
CO is the carbon dioxide in gaseous state;
2(g)
CO is the carbon monoxide in gaseous state;
(g)
ΔH is the enthalpy change .
2
© ISO 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DTS 23690:2023(E)
5 Sample preparation
MWCNT sample should be of good quality. MWCNT sample is first placed in a thermostatic vacuum
[16]
drying furnace for 2 h at 150 °C to remove unwanted volatile components. Then the sample is
transferred to a desiccator to cool down to room temperature and it is stored there until used.
6 Measurement
6.1 Apparatus
6.1.1 Thermogravimetric analyser
Thermogravimetric analyser should consist of a furnace, which is capable of heating from room
temperature to 1 000 °C or above. Heating rate during experiment should be controlled by temperature
[14]
programme set in software .
−1 −1
The linear heating rate should be controllable in the range from 1 °C min to 50 °C min . The balance
sensitivity should be at least 1 μg, and the temperature controller sensitivity less than or equal to
0,01 °C.
A crucible should be used as a sample container. The crucible is generally made of alumina, platinum,
quartz or other materials, which does not change or react under the measurement conditions.
6.1.2 Drying furnace
A drying furnace capable of being controlled heating to 150 °C or above is used.
6.1.3 Analytical balance
An analytical balance capable of weighing 0,1 mg or lower is used.
6.1.4 Desiccator
A dessicator containing a desiccant such as dried silica gel impregnated with cobalt chloride is used.
The drying agent shall not react with MWCNT samples.
6.2 Reagents
6.2.1 Inert gas
Dry, commercially available inert gas, such as nitrogen gas or argon gas, with minimum volume fraction
of 99,999 % should be used in the measurement.
6.2.2 Carbon dioxide
Dry, commercially available carbon dioxide gas with minimum volume fraction of 99,999 % should be
used in the measurement.
6.3 Measurement procedures
The thermogravimetric analyser should calibrate according to the manufacturer’s protocol to ensure
proper temperature and mass measurement.
a) Turn on the thermogravimetric analyser and wait until equilibrium reaches. Then inert gas and
carbon dioxide gas are introduced.
3
© ISO 2023 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/DTS 23690:2023(E)
b) Obtain a baseline correction file using empty crucibles at the same experiment condition.
Specifically, set the flow rate of gas to the furnace according to the instrument type. The
−1 −1
recommended inert gas flow is 10 ml min to 20 ml min and carbon dioxide gas flow is 20 ml
−1 −1 −1
min to 40 ml min ; set the heating rate as 10 °C
...
TC
Date:
ISO/DTS 23690.2
TC /SC /WG ISO/DTS 23690:2023(E)
ISO/TC 229/SC /WG 2
Secretariat: BSI
Document type:
Document subtype:
Document stage:
Document language:
---------------------- Page: 1 ----------------------
Copyright notice
This ISO document is a working draftNanotechnologies — Multiwall carbon
nanotubes — Determination of carbon impurity content by thermogravimetric
analysis
Nanotechnologies — Nanotubes de carbone multicouches — Détermination de la
teneur en impureté de carbone par analyse thermogravimetrique
First edition
Date: 2023-03-30
---------------------- Page: 2 ----------------------
ISO/DTS 23690:2023(E)
© ISO 2023
All rights reserved. Unless otherwise specified, or committee draft and is copyright-protected by ISO. While
required in the reproduction of working draftscontext of its implementation, no part of this publication may
be reproduced or committee draftsutilized otherwise in any form for use by participants inor by any means,
electronic or mechanical, including photocopying, or posting on the ISO standards development process is
permitted without prior permission from ISO, neither this document nor any extract from it may be
reproduced, stored or transmitted in any form for any other purposeinternet or an intranet, without prior
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ii © ISO 2023 – All rights reserved
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ISO/DTS 23690:2023(E)
Contents Page
Foreword . iii
Introduction . iii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
4 Principle . 2
5 Sample preparation . 3
6 Measurement . 3
6.1 Apparatus . 3
6.2 Reagents . 3
6.3 Measurement procedures . 4
7 Data analysis and interpretation of results . 4
8 Measurement uncertainty . 6
8.1 Type A uncertainty . 6
8.2 Type B uncertainty . 6
9 Test report . 6
Annex A (informative) Repeatability test: case study . 7
Annex B (informative) Reproducibility test: case study . 15
Annex C (informative) Detailed procedures for analysing TG curve . 19
Bibliography. 21
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ISO/DTS 23690:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
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collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documentsdocument should be noted. This document was drafted in accordance
with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the evidence,
validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of
this document, ISO had not received notice of (a) patent(s) which may be required to implement this
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www.iso.org/iso/foreword.htmlthe following URL: .
The committee responsible for This document iswas prepared by Technical Committee ISO/TC 229,
Nanotechnologies.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO 2023 – All rights reserved
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ISO/DTS 23690:2023(E)
Introduction
Multiwall carbon nanotubes (MWCNTs) are quasi-one-dimensional tubular carbon nanomaterials rolled
up or coaxial nested by three or more graphene sheets. The production of carbon nanotubes (CNT)
generally contains significant amounts of carbon impurities (carbon material content not in the form of
CNT, include amorphous carbon and trace amount of other types of structured carbon), which influence
the physical and chemical properties of the nanomaterial. Therefore, the measurement of carbon
impurities content in MWCNT samples is highly desired for the determination of its purity.
Several methods have been reported to characterize carbon impurities in MWCNT samples, including
transmission electron microscopy (TEM), temperature programmed oxidation (TPO) and
[ [1][2][3][4][5][6] ]
thermogravimetric analysis (TGA), etc., among which TGA can provide quantitative results . .
This technique takes use of the fact that MWCNTs are more stable than the majority of carbon impurities,
so carbon impurities less stable than MWCNTs will react firstly with carbon dioxide in carbon dioxide
atmosphere. The oxidation of carbon impurities with carbon dioxide is an endothermal process, which
prevents overheating in certain area and restrains the reaction of MWCNTs at the same time. Therefore,
[ [7][8][9][10] ]
the separation of oxidation of carbon impurities and that of MWCNTs are enhanced , , allowing
the amount of carbon impurities less stable than MWCNTs to be calculated from the mass loss in
thermogravimetric analysis.
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TECHNICAL SPECIFICATION ISO/DTS 23690:2023(E)
Nanotechnologies — Multiwall carbon nanotubes —
Determination of carbon impuritiesimpurity content by
thermogravimetric analysis
1 Scope
This document specifies a mild oxidation method to determine the content of carbon impurities (carbon
material content not in the form of CNT, include amorphous carbon and trace amount of other types of
structured carbon) less stable than multiwall carbon nanotube (MWCNT) by thermogravimetric analysis
(TGA) under carbon dioxide atmosphere.
It develops forThis document is applicable to the characterization of carbon impurities content in
MWCNT samples prepared by chemical vapour deposition (CVD). Measurement of carbon impurities in
MWCNT samples prepared by other method can refer to this document. This method is not applicable to
functionalized MWCNT samples or MWCNT samples with encapsulant species.
NOTE This method is applicable for the case of TG curve with a single-stage.
2 Normative references
The following documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO/TS 11308:2020 Nanotechnologies — Characterization of carbon nanotube samples using
thermogravimetric analysis
ISO/TS 80004-3:2020 Nanotechnologies — Vocabulary — Part 3: Carbon nano-objects
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1.1
multiwall carbon nanotube
MWCNT
multi-walled carbon nanotube
MWCNT
multiwall carbon nanotube
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ISO/DTS 23690:2023(E)
carbon nanotube composed of nested, concentric or near-concentric graphene layers with interlayer
distances similar to those of graphite.
Note 1 to entry: The structure is normally considered to be many single-walled carbon nanotubes nesting each
other, and would be cylindrical for small diameters but tends to have a polygonal cross-section as the diameter
increases.
[11]
[SOURCE: ISO/TS 80004-3:2020, clause 3.3.6] ]
3.1.2
amorphous carbon
carbon material without long-range crystalline order.
[12]
[SOURCE: IUPAC., Compendium of Chemical Terminology, 2nd ed] ]
3.2 Symbols
T temperature of the peak on DTG curve (°C)
o
w mass percentage (%) of the sample at 300 °C
300
w mass percentage (%) of the sample at temperature T
e e
ΔH is the enthalpy change .
3.23.3 Abbreviated terms
TGA thermogravimetric analysis
CVD chemical vapour deposition
CO carbon dioxide
2
MWCNT multiwall carbon nanotube
TG thermogravimetric
DTG derivative thermogravimetric
o o
T temperature ( C) at 300 C
300
o
w mass percentage (%) of the sample at 300 C
300
o
T temperature ( C) when the oxidation of carbon impurities less stable than MWCNTs is
e
complete
we mass percentage (%) of the sample at temperature Te
CO2 carbon dioxide
CVD chemical vapour deposition
DTG derivative thermogravimetric
MWCNT multiwall carbon nanotube
TG thermogravimetric
TGA thermogravimetric analysis
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ISO/DTS 23690:2023(E)
4 Principle
Thermogravimetric analysis measures the change in mass of a material as a function of temperature. In
order to accomplish this, TGA requires the precise measurements of mass, temperature and temperature
change. The change in mass of a material relates to change in composition and structure of the material.
Observed mass changes with temperature increases may result from the removal of absorbed moisture,
solvent residues, chemically bound moieties and/or the thermal or oxidative decomposition of
[11] [13]
product . Experiment carries out in an inert or oxidising atmosphere. The recorded mass change as
a function of temperature is a thermogravimetric (TG) curve. Mass change and the extent of this changes
[12] [14]
of a material in TG curve are indicators of the thermal stability of the material . Derivative
thermogravimetric (DTG) curve is a display of the first derivative of thermogravimetry data with respect
[1315]
to temperature or time .
The method specified in this document based on different reactivity of MWCNTs and carbon impurities
under carbon dioxide (CO2) atmosphere during heating. Carbon dioxide works as mild oxidant to first
oxidize carbon impurities less stable than MWCNTs. Moreover, the reaction between carbon impurities
[ [7][8][9] ]
and CO absorbs heat from environment , , which prevents local overheating, and thus enhance the
2
separation of carbon impurities and MWCNTs. The amount of carbon impurities in MWCNT samples can
be calculated from the mass loss in thermogravimetric analyzeranalyser. See the reaction formula below.
C(s) + CO2(g) → 2 CO(g); ΔH >0
where
C is carbon impurities.
C is the carbon impurities in solid state;
(s)
CO is the carbon dioxide in gaseous state;
2(g)
CO(g) is the carbon monoxide in gaseous state;
ΔH is the enthalpy change .
5 Sample preparation
MWCNT sample should be of good quality. MWCNT sample is first placed in a thermostatic vacuum drying
o [14] [16]
furnace for 2 hours h at 150 C °C to remove unwanted volatile components . Then the sample is
transferred the sample to a desiccator to cool down to room temperature and it is stored there until used.
6 Measurement
6.1 Apparatus
6.1.1 Thermogravimetric analyzeranalyser
Thermogravimetric analyzeranalyser should consist of a furnace, which is capable of heating from room
o
temperature to 1000 C1 000 °C or above. Heating rate during experiment should be controlled by
[1214]
temperature programme set in software .
o -−1 o -−1
The linear heating rate should be controllable in the range from 1 C °C min to 50 C °C min . The
balance sensitivity should be at least 1 μg, and the temperature controller sensitivity less than or equal
o
to 0,01 C °C.
A crucible should be used as a sample container. The crucible is generally made of alumina, platinum,
quartz, or other materials, which does not change or react under the measurement conditions.
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ISO/DTS 23690:2023(E)
6.1.2 Drying furnace
o
A drying furnace capable of being controlled heating to 150 C °C or above is used.
6.1.3 Analytical balance
An analytical balance capable of weighing 0,1 mg or lower is used.
6.1.4 Desiccator
A dessicator containing a desiccant such as dried silica gel impregnated with cobalt chloride is used. The
drying agent shall not react with MWCNT samples.
6.2 Reagents
6.2.1 Inert gas
Dry, commercially available inert gas, such as nitrogen gas or argon gas, with minimum volume fraction
of 99,999 % should be used in the measurement.
6.2.2 Carbon dioxide
Dry, commercially available carbon dioxide gas with minimum volume fraction of 99,999 % should be
used in the measurement.
6.3 Measurement procedures
The thermogravimetric analyzeranalyser should calibrate according to the manufacturer’s protocol to
ensure proper temperature and mass measurement.
a) Turn on the thermogravimetric analyzeranalyser and wait until equilibrium reaches. Then inert gas
and carbon dioxide gas are introduced.
b) Obtain a baseline correction file using empty crucibles at the same experiment condition. Specifically,
set the flow rate of gas to the furnace according to the instrument type. The recommended inert gas
-−1 -−1 -−1 -−1
flow is 10 ml min to 20 ml min and carbon dioxide gas flow is 20 ml min to 40 ml min ; set
o -−1
the heating rate as 10 C °C min within the temperature range from room temperature to 1000
o
C1 000 °C.
c) Weigh an appropriate amount of MWCNT sample (3 mg to 5 mg) using an analytical balance, and
transfer the sample into the crucible.
d) Before starting the measurement, keep MWCNT sample in a closed thermogravimetric
analyzeranalyser under a gas flow for at least 15 minutes, min and wait until the signal (mass,
temperature, gas flow) is stable.
e) Test the sample under the same conditions as in step b). Thermogravimetric analyzeranalyser will
automatically record the mass change of MWCNT sample with temperature.
Repeat the measurement at least three times for one MWCNT sample.
7 Data analysis and interpretation of results
TG and DTG curves of one MWCNT sample are shown in Figure 1.
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ISO/DTS 23690:2023(E)
Y
Y
1 2
110
2
100 0.0000
90
1 3
80 -0.0005
70
60 -0.0010
50
40 -0.0015
TG
30
DTG
20 -0.0020
10
4
0 -0.0025
-10
X
0 100 200 300 400 500 600 700 800 900 1000
Key
o
X temperature (in C(°C)
Y mass percentage (in %)(%)
1
o
Y2 derivative mass percentage (in %/ C(%/ °C)
o
1 w300, the mass percentage of the MWCNT sample at 300 C (in %) °C, w300 (%)
o
2 Te, the extrapolated initial temperature of MWCNT component oxidation in one MWCNT sample (in C, Te (°C)
3 we, the mass percentage of the sample at Te (in %), we (%)
o
4 To, the temperature of the peak on DTG curve (in C, To (°C)
Figure 1 — TG and DTG curves of one MWCNT sample
o o
Where, w is the mass percentage (%) of the MWCNT sample at 300 C. The mass loss below 300 C °C
300
[14] 16]
is due to the loss of volatile components . .
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ISO/DTS 23690:2023(E)
o
In the TG and DTG curves, Te is the extrapolated initial temperature ( C) of MWCNT component oxidation
in one MWCNT sample, which is defined as the temperature when the oxidation of carbon impurities less
[15]
stable than MWCNTs is completed . w is the mass percentage (%) of the sample at temperature T . T
e e e
is the intersection point between the base line and the tangent line at the maximum mass loss rate point,
where the maximum mass loss rate point is provided in DTG curve and the tangent line is obtained by
ordinary analysis software.
Calculate the content of carbon impurities in MWCNT sample by Equation Formula (1, ),
w = w – w （ (1）)
300 e
where w is the mass percentage (%) of the carbon impurities.
Conduct three independent TGA measurements for one MWCNT sample. The three measurements results
are referred as w1, w2 and w3, respectively. Calculate mass percentage of carbon impurities in MWCNT
sample according to Equation Formula (1.). Calculate the average value of the three measurements by
Equation Formula (2, ):
w ++ww
𝑤𝑤 +𝑤𝑤 +𝑤𝑤
1 2 3
1 23
w= 𝑤𝑤� = （2）
3
3
(2)
where
w
𝑤𝑤� is the average mass percentage (%) of the carbon impurities in one MWCNT sample.
Annex A and Annex B provides the case studies of repeatability and reproducibility, respectively. Annex
C provides the detail procedures for the analysis of the TG curve.
NOTE This method is applicable for the case of a TG curve with a single-stage.
Sample homogeneity should be considered. The homogeneity of MWCNT samples can be evaluated by
the constituency, thermal stability and scatter in the oxidation temperature and the residual material
[11 [13]
content in several separate TGA runs. . Errors in result calculation maycan be introduced if the
sample is non-homogeneous.
8 Measurement uncertainty
8.1 Type A uncertainty
a) 8.1.1 The uncertainty introduced by measuring method, such as measurement precision, and method
bias. It is calculated by measuring repetitive standard deviation of the reference material, which is used
for instrument calibration.
b) 8.1.2 The uncertainty introduced by measuring sample, such as the uniformity of samples, weighing,
drying and gridding. It is calculated by measuring repetitive standard deviation of the sample.
8.2 Type B uncertainty
The uncertainty is introduced by instrument calibration, such as mass calibration, and temperature
13
[ 15]
calibration .
9 Test report
The test report shall include the following information:
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ISO/DTS 23690:2023(E)
a) refer to this document; (i.e. ISO/TS 23690:XXXX);
b) sample type and name;
c) tester and the date;
d) organization, contact address and telephone number;
e) type of thermogravimetric analyzeranalyser and model;
f) test conditions, including crucible type, atmosphere, gas flow, sample mass, temperature range and
heating rate;
g) test results, including the TG and DTG curves, data and calculated content of carbon impurities in
MWCNT sample.;
h) any deviations from the procedure;
i) any unusual features observed;
j) the date of the test.
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ISO/DTS 23690:2023(E)
Annex A
(informative)
Repeatability test: Case study
A.1 General
This annex provides three cases for determination of carbon impurities less stable than MWCNTs content
by thermogravimetric analysis in CO atmosphere.
2
A.2 Sample preparation
o
Firstly, MWCNT samples placed in a thermostatic vacuum drying furnace for 2 hours h at 150 C °C. Then
transferred the samples to a desiccator to cool down to room temperature and stored there until used.
A.3 Measurement conditions
Measurement conditions were as follows:
o -−1
a) heating rate was 10 C °C min .;
o
b) set the temperature range from room temperature to 1000 C.1 000 °C;
-−1
c) set inert gas, N , flow rate as 20 ml min .;
2
-−1
d) set CO gas flow rate as 30 ml min .
2
A.4 Measurement proceduresprocedure
A.4.1 Obtain the correction baseline file obtained using empty crucible under identical experiment
condition.
A.4.2 Add an appropriate mass of the MWCNT sample into the crucible.
A.4.3 Put crucible into sample holder of thermogravimetric analyzer. analyser.
A.4.4 Set the measurement parameters according toin accordance with Clause A.3 and start the
measurement.
RepeatedA.4.5 Repeat the measurement 3three times for one MWCNT sample, and use the results to
calculate the average value of carbon impurities content.
A.5 Data analysis and interpretation of results
A.5.1 A.5.1 Sample A
TG and DTG curves of sample A showed in Figures A.1 to A.3.
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ISO/DTS 23690:2023(E)
Y Y
1
2
110
2
100 0.0000
90
3
1
80 -0.0005
70
60 -0.0010
50
40 -0.0015
TG
30
DTG
20 -0.0020
10
0 -0.0025
4
-10
X
0 100 200 300 400 500 600 700 800 900 1000
Key
o
X temperature (in C(°C)
Y mass percentage (in %)(%)
1
o
Y2 derivative mass percentage (in % C(% °C)
1 w300= = 99,70 %
o
2 Te= = 688,9 C °C
3 we= = 87,30 %
o
4 To= = 727,7 C °C
st
Figure A.1 — TG and DTG curves of sample A in the 1 first run of measurement
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ISO/DTS 23690:2023(E)
Y
1
Y
2
110
2
0.0000
100
90
1 3
-0.0005
80
70
-0.0010
60
50
-0.0015
40
TG
DTG
30
20 -0.0020
10
4
0 -0.0025
-10
X
0 100 200 300 400 500 600 700 800 900 1000
Key
o
X temperature (in C(°C)
Y1 mass percentage (in %)(%)
o
Y2 derivative mass percentage (in %/ C(%/ °C)
1 w300= = 99,70 %
o
2 T = = 681,2 C °C
e
3 w = = 87,70 %
e
o
4 T = = 725,2 C °C
o
nd
Figure A.2 — TG and DTG curves of sample A in the 2 second run of measurement
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ISO/DTS 23690:2023(E)
Y
Y
1 2
110
2
100 0.0000
90
1 3
80 -0.0005
70
60 -0.0010
50
40 -0.0015
TG
30
DTG
20 -0.0020
10
4
0 -0.0025
-10
X
0 100 200 300 400 500 600 700 800 900 1000
Key
o
X temperature (in C(°C)
Y1 mass percentage (in %)(%)
o
Y2 derivative mass percentage (in %/ C(%/ °C)
1 w300= = 99,50 %
o
2 Te= = 681,0 C °C
3 w = = 86,80 %
e
o
4 T = = 725,2 C °C
o
rd
FigureAFigure A.3 — TG and DTG curves of sample A in the 3 third run of measurement
The content of carbon impurities in the MWCNT sample was calculated according to the equation
Formulae (1) and (2) in Clause 7.
w = w – w = 99,7 % - 87,3 % = 12,4 %
1 300-1 e-1
w2 = w300-2 – we-2= 99,7 % - 87,7 % = 12,0 %
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ISO/DTS 23690:2023(E)
w3 = w300-3 – we-3= 99,5 % - 86,8 % = 12,7 %
w ++ww
12,4 %++12,0 % 12,7 %
1 23
w 12,4 %
33
𝑤𝑤 +𝑤𝑤 +𝑤𝑤 12,4%+12,0%+12,7%
1 2 3
𝑤𝑤� = = =12,4%
3 3
where
st
w is the mass percentage (%) of the carbon impurities of Sample A in the 1 run of measurement.
1
st o
w is the mass percentage (%) of Sample A in the 1 run of measurement at 300 C.
300-1
st
w is the mass percentage (%) of Sample A in the 1 run of measurement at temperature T .
e-1 e
nd
w is the mass percentage (%) of the carbon impurities of Sample A in the 2 run of measurement.
2
nd o
w is the mass percentage (%) of Sample A in the 2 run of measurement at 300 C.
300-2
nd
w is the mass percentage (%) of Sample A in the 2 run of measurement at temperature T .
e-2 e
rd
w is the mass percentage (%) of the carbon impurities of Sample A in the 3 run of measurement.
3
rd o
w is the mass percentage (%) of Sample A in the 3 run of measurement at 300 C.
300-3
rd
w is the mass percentage (%) of Sample A in the 3 run of measurement at temperature T .
e-3 e
𝑤𝑤� is the average mass percentage (%) of the carbon impurities in the measured MWCNT sample.
w is the mass percentage (%) of the carbon impurities of Sample A in the first run of
1
measurement;
w300-1 is the mass percentage (%) of Sample A in the first run of measurement at 300 °C;
w is the mass percentage (%) of Sample A in the first run of measurement at temperature T ;
e-1 e
w is the mass percentage (%) of the carbon impurities of sample A in the second run of
2
measurement;
w is the mass percentage (%) of sample A in the second run of measurement at 300 °C;
300-2
we-2 is the mass percentage (%) of sample A in the second run of measurement at temperature Te;
w is the mass percentage (%) of the carbon impurities of sample A in the third run of
3
measurement;
w is the mass percentage (%) of sample A in the third run of measurement at 300 °C;
300-3
w is the mass percentage (%) of sample A in the third run of measurement at temperature T ;
e-3 e
w is the average mass percentage (%) of the carbon impurities in the measured MWCNT
sample.
The average value of the w and the standard deviation from multiple runs are tocan be calculated (see
Table A.1). The standard deviation value of the mass percentage (%) of the carbon impurities should be
less than or equal to 1,5 %, showing repeatability of multiple TG runs.
Table A.1 — Calculations of w and Te average and standard deviations from three repeat runs of
sample A
12 © ISO 2023 – All rights reserved
= ==
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ISO/DTS 23690:2023(E)
Standard
Parameter Symbol Run 1 Run 2 Run 3 Average
deviation
The extrapolated initial
Te 688,9 681,2 681,0 683,7 4,50
temperature (℃)(°C)
The mass percentage
content (%) of the
w300 99,70 99,70 99,50 99,63 0,12
sample at 300 ℃ °C
The mass percentage
content (%) of the w 87,30 87,70
...
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